KR20100003305A - Evaporation apparatus, method of evaporation and process for producing methacrolein or (meth)acrylic acid - Google Patents

Abstract

An evaporation apparatus adapted to evaporate a portion of a liquid material containing two or more types of components for use in exothermic vapor-phase catalytic reaction and feeding the same to a reactor for the vapor-phase catalytic reaction. The evaporation apparatus comprises a can body provided at its apical part with a vapor exhaust port; an evaporation section for heating the liquid material inside and/or outside the can body to thereby evaporate the same; a column section consisting of a column containing trays and/or packing material, connected at its column bottom to the vapor exhaust port; a liquid supply tube for supply of the liquid material, provided at the middle or higher position of the column section; a vapor exhaust tube for exhausting the vapor from the apical part of the column section and feeding the same to the reactor for vapor-phase catalytic reaction; and a liquid discharge tube for discharging the liquid material lying in the can body.

Description

Evaporator and evaporation method, manufacturing method of methacrolein or (meth) acrylic acid {EVAPORATION APPARATUS, METHOD OF EVAPORATION AND PROCESS FOR PRODUCING METHACROLEIN OR (METH) ACRYLIC ACID}

The present invention provides an evaporator and an evaporation method for evaporating a part of a liquid raw material containing two or more components used in a gas phase contact reaction involving exothermic heat, and methacrolein or (meth) acrylic acid using the evaporation method. It relates to a method for producing.

This application claims priority based on patent application No. 2007-129038 for which it applied to Japan Patent Office on May 15, 2007, and uses the content here.

In the petrochemical field, organic compounds and oxygen are reacted by gas phase contact reactions to produce useful compounds. The gas phase contact reaction is generally carried out by supplying a source gas containing an organic compound and oxygen as a raw material for oxidation to a gas phase contact reactor. There are various types of reactors for the gas phase contact reaction, depending on the method of maintaining the catalyst layer, but a tubular reactor having a reaction tube in which the catalyst layer is formed is generally well known.

The raw material gas supplied to the reactor of the gas phase contact reaction is supplied from an evaporator for evaporating a liquid (liquid raw material) containing an organic compound which is usually a raw material to be converted. As an evaporator, the evaporator of the evaporator tube system which consists of a tube body which hold | maintains a liquid, and a heating apparatus which supplies a calorific value to the liquid in this tube body through a heat medium is common, For example, it connects a multi-tubular heat exchanger to the said tube body, A multi-pipe heating method for heating a liquid with a multi-tube heat exchanger, a coat sub-pipe system for heating a pipe by installing a heating coat on the outside of the pipe, and heating the pipe by installing a trace pipe on the outside of the pipe. Trace piping system etc. (for example, refer nonpatent literature 1).

In general, in the gas phase contact reaction, an appropriate catalyst is selected, and an optimum value of the reaction conditions such as the composition of the chemical component supplied to the reaction, the reaction temperature, and the pressure is selected to obtain good reaction results. By the way, when a fluctuation | variation arises in the supply amount of gas and gas composition, the reaction conditions will shift | deviate from optimal conditions, and reaction performance will worsen.

In particular, in the case of gas phase contact reactions involving exotherm, fluctuations in the heat of reaction immediately affect the reaction temperature. Therefore, reaction conditions deviate from the said optimal conditions, and reaction performance worsens. In addition, in the case where the gas phase contact reaction with exothermic heat is carried out in the tubular reactor, the heat balance of the reaction is maintained by removing the amount of heat generated in the reaction tube by a heat medium other than the reaction tube, but the reaction conditions as described above. When the fluctuation occurs, the heat balance collapses, and the heat amount accumulates exponentially in the catalyst layer. As a result, the reaction temperature further increases, and the calorific value increases. In this way, the gas phase contact reaction becomes a so-called runaway reaction due to the change in the reaction heat, which may lead to burning of the catalyst and breakage of the reaction tube in extreme cases.

When the gas phase contact reaction is carried out in the tubular reactor, the time (stay time) for the raw material gas to pass through the reaction tube of the tubular reactor is generally about 0.1 second to several seconds. Therefore, the fluctuation of the supply amount of the source gas which becomes a problem in the gas phase contact reaction is a short period of several tens of times from this stay time. Therefore, in order to stably perform the gas phase contact reaction accompanying heat generation, it is important to suppress fluctuations in the supply amount of the source gas and the gas composition in the short cycle before and after the above-mentioned stay time.

The suppression of the fluctuation of the supply amount of the raw material gas from the evaporator of the evaporator tube system to the fluctuation of the supply amount of the liquid raw material to the tube and the fluctuation of the heat amount supplied from the heat medium when evaporating the actual whole amount of the liquid raw material. It can achieve by suppressing. The supply amount of the liquid raw material and the amount of heat supplied can be controlled by a known method, and for example, it is possible to control the amount of heat by controlling the temperature and the flow rate of the heat medium.

However, when two or more kinds of components are evaporated and supplied to the reactor by evaporation, the volatilities of those components are usually different. Therefore, when a part of the liquid raw materials is evaporated (not partially evaporated), the vapor It is easy to change the composition of. Among them, when there is a large difference in volatility between the components contained in the liquid raw material and the components to be evaporated and supplied to the reactor and the components left without evaporation (such as impurities), the liquid composition and the gas composition differ greatly. The gas composition fluctuates greatly when external confusion enters.

Therefore, the part of the liquid raw material containing 2 or more types of components used for the gas phase contact reaction with exothermic reaction does not produce fluctuation of the supply amount or composition of a gas phase contact reaction to the reactor in the short period before and behind the said stay time, There is a need for an evaporator and evaporation method capable of stably evaporating.

Non Patent Literature 1: Introduction to Process Design, pp. 63-72, Institute of Chemical Engineering, August 1973

Disclosure of Invention

Problems to be Solved by the Invention

The present invention provides an evaporator and an evaporation method capable of stably evaporating a part of a liquid raw material containing two or more components used in a gas phase contact reaction involving exotherm, and methacrolein or (meth) acrylic acid using the evaporation method. The object of this invention is to provide a manufacturing method.

Means to solve the problem

This invention which solves the said subject has the following aspects.

[1] An evaporator for evaporating a part of a liquid raw material containing two or more components used in a gas phase contact reaction with exothermic heat and supplying it to the reactor for the gas phase contact reaction, having a vapor outlet at the top And an evaporation unit for heating and evaporating the liquid raw material inside and / or outside of the pipe body, a shelf end connected to a vapor outlet, and / or a packing material. A tower portion comprising a tower, a liquid supply pipe for supplying the liquid raw material to a position above the middle portion of the tower portion, a vapor derivation tube for extracting steam from the top of the column portion and supplying it to the reactor for the gas phase contact reaction, and the tube body And a liquid discharge pipe for discharging the liquid raw material therein.

[2] The evaporator according to [1], wherein the tower portion is constituted by a shelf stage having a shelf stage of 1 to 10 stages or a packed column having a packed length corresponding to a theoretical stage of 0.5 to 5 stages.

[3] The evaporator according to [1] or [2], which is provided with a heat medium blowing pipe for directly injecting a heat medium into the pipe.

[4] An evaporation method for evaporating a part of a liquid raw material containing two or more components used in a gas phase contact reaction with exothermic heat, wherein the liquid raw material is subjected to the evaporator according to any one of [1] to [3]. Evaporation method characterized by having the process of supplying.

[5] The evaporation method according to [4], which has a step of directly blowing the component or vapor thereof used in the gas phase contact reaction into the tube as the heat medium.

[6] Among all the components in which the liquid raw material and the heat medium directly blown into the tube are combined, the volatilization k _l of the highest volatility component among the components having a substantial concentration that does not evaporate, and among the components having a substantial concentration to evaporate. The evaporation method as described in [5] whose ratio (k _l / k _m ) with the volatilization k _m of the lowest volatile component is 1.5 or more.

[7] The evaporation method according to [5] or [6], wherein the liquid raw material contains a tertiary butyl alcohol or (meth) acrolein and uses water vapor as the heat medium.

[8] Methacrolein or (meth) acrylic acid comprising the step of evaporating a liquid raw material containing tert-butyl alcohol or (meth) acrolein by the evaporation method according to any one of [4] to [7]. Method of preparation.

Effects of the Invention

According to the evaporator and the evaporation method of the present invention, a part of the liquid raw material containing two or more components used in the gas phase contact reaction with heat generation can be stably evaporated.

The evaporation method of the present invention is suitably used for the method for producing methacrolein or (meth) acrylic acid.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram which shows one Embodiment (multi-tubular heat exchanger system) of an evaporation part.

It is a schematic block diagram which shows one Embodiment (coat type) of an evaporation part.

It is a schematic block diagram which shows one Embodiment (trace piping system) of an evaporation part.

It is a schematic block diagram which shows one Embodiment (shelf column type) of an evaporator.

Fig. 5 is a schematic configuration diagram showing one embodiment of the evaporator (charge tower type).

Explanation of the sign

11... Evaporation section 12... Tube

12a... Steam outlet, 12b ... Liquid outlet

13... Liquid discharge pipe, 14... Shell and tube heat exchanger

15... Tubing, 16... pipe

17... Pump, 18... Heating medium supply pipe

19... Heating medium discharge pipe, 21... Evaporator

22... Coat, 23... Heating medium supply pipe

24... Heating medium discharge pipe, 31... Evaporator

32... Trace piping, 33... Heating medium supply pipe

34... Heating medium discharge pipe, 41... evaporator

42... Evaporation section 43. Shelf

44... Steam duct, 45... Heat medium blowing pipe

46... Liquid supply pipe, 47... Liquid supply pipe

51... Evaporator, 52... Charging tower

53... Liquid supply pipe

Best Mode for Carrying Out the Invention

<Evaporator>

The evaporator of the present invention includes an evaporator having a pipe having a vapor outlet at the top, a tower having a bottom connected to the vapor outlet of the pipe, a liquid supply pipe connected to a position at or above the middle of the tower, and a top of the tower. A connected steam outlet pipe and a liquid discharge pipe connected to the pipe are provided.

In such an evaporator, when a liquid raw material is supplied from a liquid supply pipe, the liquid raw material is first introduced into a position above the middle portion of the column portion and flows down into the column portion, and is introduced into the tubular body through the steam outlet at the bottom of the column portion. do. Then, the heating mechanism in the pipe receives the amount of heat required to evaporate a portion of the liquid raw material through the heat medium and evaporates. The steam in the tube moves to the tower through the steam outlet, rises up in the tower, and is led from the steam outlet pipe connected to the top, and is supplied to the reactor for gas phase contact reaction. In addition, in the liquid raw material, components left without evaporation are discharged out of the evaporator from the liquid discharge pipe. An evaporation part means here the part which combined the tube body and a heating mechanism, and does not contain a tower part.

The evaporation section includes a tube body having a steam outlet at the top and a liquid outlet at the bottom, and a heating mechanism for supplying heat to the liquid present in the tube through the heat medium. In addition, a liquid discharge pipe is connected to the liquid discharge portion.

As a heating mechanism, what is a mechanism which heats and evaporates a raw material liquid in the inside and / or outside of a tubular body can be used. As a heating mechanism of such an internal heating type or an external heating type, one similar to that used in the conventional evaporation tube system can be used. As an external heating type | mold, a multi-tubular heat exchanger is mentioned, As an internal heating type | mold, an outer coat, a trace piping, etc. are mentioned. Among these, a multi-tube heat exchanger is preferable because of the large amount of liquid raw material that can be treated.

As an evaporation unit using a multi-tubular heat exchanger as a heating mechanism, a pipe body, a pipe through which the heat exchanger derives a liquid raw material from the liquid extracting part of the pipe and sends it to the heat exchanger, and a pipe which introduces the liquid raw material heated by the heat exchanger and the vapor into the pipe body The connected thing is mentioned. As such an evaporation unit, there are a thermosyphon system in which a pump is not provided between the heat exchanger and the tube, and a forced circulation system in which a pump is provided between the heat exchanger and the tube. A forced circulation system is preferable from the viewpoint of the stability of the amount of heat supplied to the liquid raw material.

As a heating mechanism of that excepting the above, the heat medium blowing pipe which blows a heat medium directly in a pipe body is mentioned. By providing a heat medium blowing pipe, when using the component used for the said gas phase contact reaction as a heat medium or its vapor | steam, the said heat medium can be blown directly into the liquid raw material in a pipe body.

These heating mechanisms may be used individually by 1 type, and may use 2 or more types together.

1 to 3 each show one embodiment of the evaporation section to which the liquid discharge pipe used in the present invention is connected.

1 is a schematic configuration diagram of an evaporator 11 having a tubular heat exchanger. In the evaporation section 11, the tube body 12 has a vapor ejection opening 12a at the top thereof, and a liquid ejecting portion 12b at the bottom thereof. The liquid discharge pipe 13 is connected to the liquid discharge part 12b, and the component which does not evaporate among the liquid raw materials in the pipe body 12 can be discharged out of the system.

The tubular body 12 is attached with the heating mechanism provided with the multi-tubular heat exchanger 14 as a heating mechanism. The heating mechanism includes a heat exchanger (14), one end of which is connected to the liquid discharge pipe (13), the other end of which is connected to an inlet of the heat exchanger (14), and one end of the heat exchanger (14). The pipe 16 connected to the outlet and connected to the trunk portion of the pipe body 12 is composed of a heat medium supply pipe 18 for supplying a heat medium, and a heat medium discharge pipe 19 for discharging the heat medium.

A pump 17 is provided on the pipe 15, and the liquid raw material in the pipe body 12 passes from the pipe body 12 to the liquid discharge pipe 13, the pipe 15, the heat exchanger 14, and the pipe 16. It is possible to force circulation to the tubular body 12. On the other hand, when the evaporator 11 is a thermosyphon system, the pump 17 may not be provided.

The heat medium supply pipe 18 and the heat medium discharge pipe 19 are connected to the heat exchanger 14, respectively, and the heat exchanger 14 can supply the amount of heat required for evaporation through the heat medium to the liquid raw material. The heat medium supply pipe 18 may be provided with a control valve for adjusting the liquid raw material supply amount.

2 is a schematic configuration diagram of an evaporator 21 having a coat as a heating mechanism. In addition, in FIG.2-3, the component corresponding to the component shown in FIG.1 is attached | subjected with the same code | symbol, and the detailed description is abbreviate | omitted.

The evaporation unit 21 is a heating mechanism, and is composed of a coat 22, a heat medium supply pipe 23 for supplying a heat medium to the coat 22, and a heat medium discharge pipe 24 for discharging the heat medium in the coat 22. .

The outer coat 22 is attached to the outside of the tube body 12, and by heating the tube body 12 through the heat medium, the amount of heat required for evaporation can be supplied to the liquid raw material accommodated in the tube body 12.

3 is a schematic configuration diagram of an evaporator 31 having a trace pipe as a heating mechanism. The evaporator 31 is a heating mechanism, which includes a trace pipe 32, a heat medium supply pipe 33 for supplying a heat medium to the trace pipe 32, and a heat medium discharge pipe 34 for discharging the heat medium in the trace pipe 32. It is composed.

The trace pipe 32 is attached to the outside of the tubular body 12, and the heat quantity required for evaporation can be supplied to the liquid raw material accommodated in the tubular body 12 by heating the tubular body 12 through a heat medium.

The tower part to which the tower bottom is connected to the steam outlet 12a of the pipe body 12 is comprised by the tower containing a shelf end and / or a filler. The tower including the shelf is called the shelf tower, and the tower containing the filling is called the packed column. The top portion may include both the shelf end and the filling material.

As the shelf column and the packed column, it is preferable to have the same structure as the shelf column and the packed column which are generally used for purification and distillation.

Examples of the shelf steps used in the shelf tower include a sieve tray having a bank, a sieve tray without a bank, a turbo grid, and the like. It is preferable to select these trays suitably according to the property of the liquid raw material to handle. For example, a sheave tray without a weir is preferable when the liquid raw material contains a polymerizable substance. On the other hand, a polymerizable substance is a compound which has a polymerizable functional group (for example, vinyl group etc.).

As a packing material used for a packed column, the irregular packing used for an absorption tower or a distillation column, or a regular packing is mentioned. It is preferable to select these fillers suitably according to the property of the liquid raw material to handle. For example, regular fillers are suitable when the liquid raw material is a polymerisable material.

It is preferable that the top part has a structure with a small amount of liquid retention inside the top part. As a tower part of such a structure, the tower part comprised from the shelf tower | column of 1-10 stages or the packed column of the filling length corresponding to the theoretical stage of 0.5-5 stages is mentioned.

Here, the charging length in a packed column is the height of the part (charge part) in which the packing material is filled in the tower part, and when there exist multiple charge parts, it is the sum total of the height of each charge part.

The upper limit of the number of stages of the shelf column and the theoretical number of stages of the packed column are selected from the point which does not unnecessarily raise the pressure inside a pipe | tube, and suppresses installation cost. As for the stage of a shelf column tower, 3-7 stages are more preferable. As for the theoretical stage of a packed tower, 1.5-3.5 stage are more preferable.

In this invention, the liquid supply pipe which supplies a liquid raw material to the position more than the intermediate part of the said tower part is connected. Here, the middle part of the top part is a part in which a shelf end or a charging part is provided, and in a shelf end tower, the middle part is a middle part from the lower end of the shelf end arrange | positioned at the lowermost to the upper end of the shelf end installed in the uppermost part. The middle part is from the lower end of the charging part arranged in the lowermost part to the upper end of the charging part provided in the uppermost part. In addition, "a position more than the middle part of a top part" is a position between the lower end of an intermediate part, and the top part of a top part.

The connection position of the liquid supply pipe is preferably a position (upper) between the upper end and the upper end of the intermediate portion. The number of liquid supply pipes may be one, and may be two or more. When two or more liquid supply pipes are provided, the components used for the gas phase contact reaction with heat generation can be supplied from the respective liquid supply pipes to the tower. The control valve for adjusting the liquid supply amount may be provided in the liquid supply pipe.

The top of the tower section is connected with a steam lead-out pipe for drawing steam in the tower section. The other end of the steam outlet pipe is connected to a reactor for gas phase contact reaction, and the steam in the column can be supplied to the reactor.

4 to 5 show preferred embodiments of the evaporator of the present invention. In addition, in FIGS. 4-5, the component corresponding to the component shown in FIG. 1 is attached | subjected with the same code | symbol, and the detailed description is abbreviate | omitted.

The evaporator 41 shown in FIG. 4 is provided with the evaporation part 42 and the shelf end tower 43 used as a top part, and the vapor | steam extraction pipe 44 is connected to the top part of the shelf end tower 43. As shown in FIG. The evaporation part 42 has a structure in which the medium blowing pipe 45 which blows in the heat medium in the pipe | tube 12 as a heating mechanism is provided in addition to the structure of the evaporation part 11 of the structure shown in FIG. In the evaporator 42, the liquid discharge pipe 13, the heat medium supply pipe 18, and the heat medium blow pipe 45 respectively control valves 13a and 18a for adjusting the liquid raw material discharge amount, the heat medium supply amount, and the heat medium blowing amount. 45a) is installed.

The shelf tower 43 is attached to a steam outlet (not shown) of the tube body 12. In the shelf tower 43, a plurality of trays 43a are provided. The liquid supply pipes 46 and 47 are connected to the middle part (the position of M in FIG. 4) and the upper part of the shelf tower 43, respectively, and the control valves 46a and 47a which adjust the liquid raw material supply amount are provided, respectively. have.

The evaporator 51 shown in FIG. 5 differs from the evaporator 41 in that the top portion is constituted by the packed column 52. The two charging parts 52a are provided in the charging tower 52. The liquid supply pipes 53 and 54 are connected to an upper portion than the middle portion (the position of M in FIG. 4) of the packed column 52, and the liquid supply pipes 53 and 54 are respectively provided with control valves for adjusting the liquid raw material supply amount ( 53a and 54a are provided.

When using a vaporizer of the present invention to evaporate a part of the liquid raw material containing two or more components used in the gas phase contact reaction with heat generation, necessary auxiliary agents (antipolymerization agent, antifoaming agent, etc.) from the properties of the liquid raw material to be handled ), A supply pipe for auxiliary drift can be provided at an appropriate position of the evaporator of the present invention. In addition, in the evaporator of this invention, you may provide auxiliary equipments, such as a meter for various measurement control, in arbitrary positions, such as an evaporation part, a tower part, a liquid supply pipe, and a vapor discharge pipe.

Generally, when evaporating the liquid raw material containing 2 or more types, the evaporation operation | movement which does not evaporate most of the high boiling point thing may be performed. Since such evaporation operation does not require precise distillation separation operation, separation by so-called single distillation by a tube is sufficient. However, in the gas phase contact reaction, fluctuations in the composition and the supply amount of the source gas in a short time period are not allowed as described above. If a liquid raw material containing two or more components used in the gas phase contact reaction is evaporated, a part of which is evaporated and a part thereof is not evaporated, the conventional evaporator type distillation machine is susceptible to external disturbances, and thus is short-lived. It is difficult to control fluctuations in vapor composition or evaporation in the cycle.

On the other hand, in the evaporator of this invention, a tower part is provided on a tubular body, and a liquid supply pipe is connected to the specific position of the said tower part, and contains two or more types of components used for the gas phase contact reaction with heat generation. Evaporation of a liquid raw material can be performed stably. When a part of liquid raw material is evaporated using the evaporator of this invention, a liquid raw material which flows down in a tower part, and the vapor | steam rising up in a tower part come into contact, and a distillation function acts, and a vapor composition and a liquid composition come close to each other. This is considered to be because the fluctuations in the vapor composition are alleviated.

Therefore, the evaporator of the present invention is useful as an evaporator for evaporating a liquid raw material containing two or more kinds of components used in the gas phase contact reaction, and among them, in the composition of a component in which the liquid raw material and the heat medium blown into the tube are combined, Volatilization k ₁ of the highest volatility component (non-evaporation component) having a substantial concentration, and volatility k _m of the lowest volatility component (evaporation component) having a substantial concentration of evaporation. It is suitable when a liquid raw material having a ratio (k ₁ / k _m ) of 1.5 or more and a heat medium blown into the tube body are used.

Here, having a substantial concentration means that it is the concentration of the component which needs to manage the density | concentration in an evaporation component or a non-evaporation component, and means that it is a density | concentration more than an analysis detection limit concentration at least. The least volatile component of the evaporating component having a substantial concentration, or the most volatile component of the non-evaporating component having a substantial concentration is called the limit component.

<Evaporation method>

The evaporation method of the present invention is an evaporation method for evaporating a part of the liquid raw material, and has a step of supplying the liquid raw material to the evaporator of the present invention. When the liquid raw material is supplied from the liquid supply pipe to the evaporator of the present invention, the liquid raw material is first introduced into a position above the middle part of the column, and is introduced into the tube through the steam outlet through the vapor outlet at the bottom of the column. Then, the heating mechanism in the evaporation unit receives the amount of heat required to evaporate a portion of the liquid raw material through the heat medium and evaporates. The vapor in the tube moves to the tower through the steam outlet, is led up from the steam outlet pipe connected to the top of the tower, and supplied to the reactor for gas phase contact reaction. In addition, in the liquid raw material, the components left without evaporation are discharged out of the evaporator from the liquid discharge pipe.

In the evaporation method of this invention, the component used for the said gaseous-phase contact reaction as the said heat medium, or its vapor is blown from the said heat medium blowing pipe using the thing provided with the heat medium blowing pipe which blows a heat medium directly in a pipe | tube as an evaporator. It is preferable to perform a process. In the gas phase contact reaction with exothermic heat, water is often added as a diluent in the source gas in order to suppress the temperature rise of the catalyst layer in the reactor or to improve the selectivity and the life of the catalyst. In this case, it is effective to directly inject the required amount of water or water vapor into the liquid raw material in the tube by using water vapor as the heat medium.

At this time, as a heating mechanism of the evaporation unit, a heat medium blowing pipe may be used alone, or other heating mechanisms (multi-tubular heat exchanger, envelope, trace piping, etc.) may be used in combination. When the amount of heat required for evaporation is larger than the amount of water or water vapor blown, it is preferable to use another heating mechanism, especially a heat exchanger.

As described above, the evaporation method of the present invention, in particular in the composition of the component that combines the liquid raw material and the heat medium blown into the tube, has the highest volatilization of the component (non-evaporation component) having a substantial concentration which does not evaporate. The liquid raw material having a ratio (k _l / k _m ) of the lowest volatility k _m of the lowest volatility component (evaporation component) of the volatilization k _l and the substantial concentration of evaporation (evaporation component), and the heat medium blown into the tube Suitable for evaporation. Here, "having a substantial concentration" is as described above.

In the composition of the component which combined the liquid raw material which consists of n components, and the heat medium blown into a pipe | tube, 1st component, 2nd component,... When defined as the n-th component, the volatilization k _i of the i-th component (i is an integer of 1 to n) constituting the liquid raw material and the heating medium blown into the tubular body is defined by the following formula (1).

k _i = p _i / x _i . … (One)

In said formula (1), x _i shows the mole fraction of i component of an evaporator internal liquid, and p _i shows the partial pressure of i component in the gas in equilibrium with x _i .

Among the n components, the m component (m is a component having a substantial concentration at an integer of 1 to n) in the first component is evaporated to be an evaporation component used for the gas phase contact reaction, and the n component (l) in the first component is used. Is a non-evaporation component, the lowest volatilization component among the evaporation components is the mth component, and the volatility is k _m . The highest volatilization component among the non-vaporization components is the first component, and the volatilization degree is k _l . The evaporation method of the present invention is suitably used in the case of evaporating the liquid raw material and the heat medium blown into the tube having a ratio of k _l and k _m (k _l / k _m ) of 1.5 or more.

Thus, when evaporating the liquid raw material and the heat medium blown into a pipe | tube with which the volatility of both limit components (the mth component and a 1st component) are separated, so-called single distillation using the conventional evaporation tube system in evaporation in a pipe | tube is carried out. The liquid composition and the vapor composition are significantly different, and any external disturbances cause the evaporation composition to fluctuate greatly. However, in the present invention, by using the evaporator of the present invention, the liquid composition and the vapor composition are close to each other due to the distillation effect inside the column, so that the variation in composition due to external confusion is alleviated.

The evaporation method of the present invention is further preferably used for evaporation of a liquid raw material in which k _l / k _m is 2 or more. The volatilization degree of each component is calculated | required by Formula (1) mentioned above.

As an example of a gas phase contact reaction involving exothermic heat using a liquid raw material evaporated by the evaporation method of the present invention, a gas phase contact reaction of a tertiary butyl alcohol or (meth) acrolein with oxygen (a gas phase catalytic oxidation reaction) have. Methacrolein or methacrylic acid is synthesize | combined by the gas phase catalytic oxidation reaction of a tertiary butyl alcohol. In addition, methacrylic acid is synthesized by gas phase catalytic oxidation of methacrolein. In addition, acrylic acid is synthesized by vapor phase catalytic oxidation of acrolein. The evaporation method of the present invention is particularly suitable for the case of using water containing tertiary butyl alcohol or (meth) acrolein as the liquid raw material and using water vapor as the heat medium.

Representative examples of the source gas composition of the gas phase catalytic oxidation of tertiary butyl alcohol include inert gases such as tertiary butyl alcohol, oxygen, and water of 5%, 10%, 5%, and nitrogen, respectively. It is That is, water is not involved in the direct reaction in the gas phase catalytic oxidation of tertiary butyl alcohol, but it has an effect such as dilution of the reaction gas and can be said to be one of the necessary components in the source gas.

Tertiary butyl alcohol, on the other hand, is synthesized by a hydration reaction from an isobutene-containing carbon 4 fraction, which is one of the naphtha cracking products, or from a by-product gas of isobutene-containing carbon 4 from a fluid catalytic cracking plant, the product of which In addition to the tertiary butyl alcohol, impurities include water, a multimer of isobutene, and a secondary butyl alcohol.

As mentioned above, since water is essential in the source gas of the gas phase catalytic oxidation reaction of tertiary butyl alcohol, as a liquid raw material used for the gas phase catalytic oxidation reaction of tertiary butyl alcohol, the synthetic | combination agent normally synthesized as mentioned above is mentioned. Tertiary butyl alcohol is used as is without water separation. That is, the liquid raw material used for the gas phase catalytic oxidation of tertiary butyl alcohol is usually composed of tertiary butyl alcohol, water, a multimer of isobutene, secondary butyl alcohol and the like. This liquid raw material contains a low concentration but contains impurities such as a multimer of isobutene, a secondary butyl alcohol, and a high boiling point caused by a catalyst of a hydration reaction. Since these impurities are undesirable in the catalyst or product quality of the gas phase catalytic oxidation reaction, it is preferable to discharge them without evaporating in an evaporator.

The content rate of the tertiary butyl alcohol and water in the said liquid raw material changes with the manufacturing process of a tertiary butyl alcohol. Compared with the target source gas composition suitable for the gas phase catalytic oxidation reaction of the tertiary butyl alcohol, when there is much moisture in the liquid raw material, part of the water is separated without evaporation in the evaporator. On the contrary, when there is little moisture in a liquid raw material, even if water is added to a liquid raw material in an evaporator, or water vapor is directly blown in a pipe | tube as a heat medium from the said heat medium blowing piping using the thing provided with the said heat medium blowing piping as an evaporator. good.

In this example, among the evaporating components, the lowest volatile component having a real concentration is water, and the highest volatile component having a substantial concentration among the non-evaporating components is tertiary butyl alcohol. The non-volatile degree in the composition to which the amount of water vapor blown into the liquid raw material and the tube is added is about 2.5. In the conventional evaporator, the fluctuation of the vapor composition due to external confusion is large, but according to the present invention, the liquid raw material is stable. Can be evaporated.

In the case of the process of synthesizing (meth) acrylic acid by the gas phase catalytic oxidation reaction of (meth) acrolein, as shown below, a stable evaporation can be carried out using the evaporation method of the present invention.

Representative of the source gas composition of the gas phase catalytic oxidation reaction of (meth) acrolein is (meth) acrolein, oxygen, and water of 5%, 10%, and 10%, respectively. Water is not directly involved in the gas phase catalytic oxidation reaction of (meth) acrolein, but has an effect such as dilution of the reaction gas, and it can be said that water is one of the necessary components in the source gas. On the other hand, (meth) acrolein can be produced by the gas phase catalytic oxidation reaction of tertiary butyl alcohol and / or isobutene, propylene and oxygen, but a typical example of the reaction product composition is a low boiling point such as acetone. ) Is 4%, (meth) acrolein is 86%, and water is 10% (all moles in the above).

As mentioned above, since water is essential in the source gas of the gas phase catalytic oxidation reaction of (meth) acrolein, as a liquid raw material used for the gas phase catalytic oxidation reaction of (meth) acrolein, the (meth) acrolein synthesis reaction is usually carried out as mentioned above. By-product water is used as is. In addition, (meth) acrolein contains an inhibitor or a polymer in small amount. That is, the liquid raw material used for the gas phase catalytic oxidation of (meth) acrolein is usually evaporated in an evaporator because a small amount of high boiling point such as an inhibitor or a polymer is contained in addition to the low boiling point such as (meth) acrolein, water and acetone. It is preferable to discharge, without letting it happen. As a result, not only stable evaporation can be carried out, but also the (meth) acrolein concentration in the tube is lower than that of the conventionally used evaporation tube system, and the loss of the main raw material can be prevented. There is an advantage that the generation of the polymerized product at is suppressed and stable operation can be performed.

The ratio of water to (meth) acrolein in the liquid raw material is lower than the ratio of water to (meth) acrolein in the steam supplied to the oxidation reactor. Therefore, when water and / or steam are added to the liquid raw material in the evaporator of the present invention when evaporating the liquid raw material containing (meth) acrolein, the ratio of water to (meth) acrolein in the vapor supplied to the oxidation reactor is easily facilitated. Can be increased.

In this example, the lowest volatile component having a substantial concentration among the evaporating components is water, and the highest volatile component having a substantial concentration among the non-vaporizing components is (meth) acrolein. In addition, the non-volatile degree in the composition which added the amount of water vapor blown in a liquid raw material and a pipe | tube is about 4, The fluctuation of a vapor composition is large in the conventional evaporator, However, According to this invention, this liquid raw material can be evaporated stably. have.

Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example.

Example 1

In the process of synthesizing methacrolein by gas phase catalytic oxidation with tertiary butyl alcohol and oxygen, the raw material gas supplied to the reactor in which the reaction is carried out is produced using an evaporator 41 having the configuration shown in FIG. 4. did.

In the evaporator 41, a longitudinal shell-and-tube heat exchanger is used as the heat exchanger 14, and heating is performed by using a thermosyphon system (not using the pump 17) using water vapor having a pressure of 0.3 MPa as a heat medium. Carried out. As the shelf tower 43, a shelf tower provided with a sheave tray of five tiers was used.

The composition of the liquid raw material used for the said vapor phase catalytic oxidation reaction was 60 mol%, 39.9 mol%, and 0.1 mol% of high boiling points, such as a tertiary butyl alcohol, water, and a secondary butyl alcohol, respectively.

Among the evaporating components, the lowest volatile component having a real concentration is water, and the highest volatile component having a substantial concentration among the non-vapor components is tertiary butyl alcohol. In addition, the specific volatility in the composition added with the amount of water vapor blown from the liquid raw material and the tube was about 2.5.

The liquid raw material was supplied to the liquid supply pipe 47 (above the uppermost tray) of the evaporator 41. 20 mol% of water vapor with respect to the liquid raw material is directly blown from the heat medium blowing pipe 45 into the pipe body 12, and is heated by a heat exchanger 14 to evaporate the liquid raw material, and the vapor is fed into the shelf column 43. It led out through the steam extraction pipe 44 of the top part, and supplied it to the reactor.

In the liquid raw material supplied, 0.01 mol% of tertiary butyl alcohol and 2 mol% of water were removed from the liquid discharge pipe 13 without evaporating.

For the control of the supply amount of the liquid raw material, the amount of liquid drawn out of the non-evaporation component in the raw material liquid, and the amount of water vapor blown into the tubular body 12, a flow controller is provided in the evaporator 41 by a calculator control system. I made it possible. The blowing amount and the heating amount of the water vapor used as the heat medium were provided with a flow rate controller by a calculator control system so as to be within an error of ± 0.5%. On the other hand, the set value of the flow rate control of this water vapor | steam was employ | adopted the control system which changes setting smoothly by the cascade control by the internal liquid surface of the tubular body 12. As shown in FIG.

The reactor for supplying the oxidation reaction raw material steam is a multi-tube reactor using a steel pipe (reaction tube) having an inner diameter of 25 mm and a length of 5 m. The outside of the reaction tube is provided with a mechanism for circulating nitrate to remove the heat of reaction. As the catalyst layer in the center of the reaction tube, a known oxide catalyst of molybdenum-cobalt-nickel was used. The reactor was provided with a thermocouple so that the temperature distribution in the flow direction of the source gas can be measured.

The composition (reactor inlet composition) of the vapor (raw material gas) supplied from the evaporator was 5, 10, 5 (mol%) of tertiary butyl alcohol, oxygen, and water, and the other inert gas components. The gas temperature at the inlet of the catalyst bed was 295 ° C., and the pressure was 0.14 MPa.

In this way, the vapor from the evaporator 41 was supplied to the reactor, gas phase catalytic oxidation reaction was carried out, and methacrolein was synthesize | combined.

As a result, the deviation between the maximum temperature of the catalyst layer of each reaction tube and the nitrate temperature was not seen in a short time, and a very stable state could be maintained. Moreover, the difference between the 100 reaction tubes which measured the temperature distribution was also small, and the average value was 30 +/- 2 and maintained the favorable state.

Comparative Example 1

The shelf end tower 41 is not provided, except that the liquid supply pipe 47 is directly connected to the trunk portion of the pipe body 12, and the steam outlet pipe 44 is connected to the steam outlet of the pipe body 12. Methacrolein was synthesize | combined like Example 1 using the evaporator of the same structure as the evaporator 41 used in Example 1.

As a result, the temperature difference between the maximum temperature of the catalyst layer of each reaction tube and the nitrate was large, and the variation in the short time was 30 ± 7 ° C., and a stable state could not be maintained. In five reaction tubes among the 100 reaction tubes in which the temperature distribution was measured, the temperature difference between the highest temperature portion of the catalyst layer and the nitrate became 45 ° C. or higher, and the so-called runaway reaction state caused the catalyst to lose activity.

According to the evaporator and the evaporation method of the present invention, since a part of the liquid raw material containing two or more of the components used in the gas phase contact reaction with heat generation can be evaporated stably, Fluctuations in gas composition can be suppressed.

Claims (8)

 An evaporator for evaporating a portion of a liquid raw material containing two or more components used in a gas phase contact reaction with exothermic heat and supplying it to the reactor of the gas phase contact reaction, An evaporation unit having a pipe body having a vapor outlet at the top, for evaporating the liquid raw material by heating the inside and / or outside of the pipe body; A tower portion configured of a tower including a shelf end and / or a filler having a tower bottom connected to the steam outlet, A liquid supply pipe for supplying the liquid raw material to a position above a middle portion of the column; A vapor derivation tube for deriving steam from the top of the column and supplying the vapor to the reactor of the gas phase contact reaction, and Liquid discharge pipe for discharging the liquid raw material in the tube Evaporator comprising a. The method of claim 1, The evaporator of which the said tower part consists of a shelf tower | column with a shelf stage of 1-10 stages, or a packed column of packed length corresponding to the theoretical stage of 0.5-5 stages. The method according to claim 1 or 2, An evaporator having a heat medium blowing pipe for directly injecting a heat medium into the pipe. An evaporation method for evaporating a part of a liquid raw material containing two or more components used in a gas phase contact reaction with exothermic heat, Evaporating method characterized by having the process of supplying the said liquid raw material to the evaporator in any one of Claims 1-3. The method of claim 4, wherein The evaporation method which has a process which blow | pours the component used for the said gaseous-phase contact reaction, or its steam directly in the said tube body as said heat medium. The method of claim 5, wherein Volatilization degree k _l of the highest volatility component among the components which have the substantial concentration which does not evaporate among all components which combined the said liquid raw material and the heat medium directly injected into the said pipe | tube, and the volatility degree among the components which have a substantial concentration to evaporate. The evaporation method in which the ratio (k _l / k _m ) to the volatility k _m of the lower component is 1.5 or more. The method according to claim 5 or 6, An evaporation method using water vapor as said heat medium, using what contains tertiary butyl alcohol or (meth) acrolein as said liquid raw material. A process for producing methacrolein or (meth) acrylic acid comprising evaporating a liquid raw material containing tertiary butyl alcohol or (meth) acrolein by the evaporation method according to any one of claims 4 to 7. .

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